He noticed the richer children tended to be more possessive with their toys, whereas children in poorer countries were more accustomed to sharing with neighborhood playmates.

The toys the children decided to display also revealed a lot about their parents — whether it was a taxi driving mother who gave her son miniature cars or an Italian farmer whose daughter was photographed with her pastel-colored plastic farm equipment.

But wherever the kids lived, one thing was universal: They just wanted to play.